Mandrel locking unit for printing roller mandrels in a rotary printing machine

ABSTRACT

The present invention relates to a mandrel-locking unit ( 1 ) for a rotary printing machine in which ( 1 ) a mandrel-mounting element ( 9 )—preferably, a sleeve—surrounds print roller mandrels ( 13 ) in its inner bearing ( 11 ) for mounting the mandrel-supporting surface ( 12 ) and into which ( 1 ) the mandrel-mounting element ( 9 ) can be slid in such a manner that the mandrel-supporting surface ( 12 ) is released by the sliding movement and which ( 1 ) comprises a pressurizing medium cylinder ( 2 ) that provides the force required for the sliding movement and that ( 2 ) has a piston ( 4 ), which ( 4 ) delimits the pressure chamber ( 3 ) of the pressurizing medium cylinder ( 2 ) at a boundary surface and which ( 4 ) is in contact with the mandrel-mounting element ( 9 ) at a connecting point and conveys to the mandrel mounting element ( 9 ) the pressure required for the sliding movement by means of the connecting point. The mandrel-locking unit ( 1 ) according to the invention is characterized in that the distance between the boundary surface and the connecting point is smaller than the maximum stroke of the piston ( 4 ) in the pressurizing medium cylinder ( 2 ).

The present invention relates to a mandrel-locking unit in accordancewith the preamble of the main claim 1.

The processing of different print jobs frequently necessitates thereplacement of printing plates. Therefore print rollers are known fromthe prior art that comprise print roller mandrels whose print rollersleeves, the so-called sleeves—can be pulled off and put back on again.In order to replace the sleeves without having to remove the printroller from the printing machines, the print roller mandrels arearranged such that their one end usually floats. The free end isembraced by a bearing during the printing operation. Within theframework of the present invention, all rollers involved in a printingprocess are referred to as print rollers.

The patent application DE 197 05 369 A1 illustrates, for example, aprinting machine of such type. A bearing block is assigned to everyroller involved in the printing process. The bearing block can bedisplaced in relation to the roller after the connection of the bearingto the roller is released. The actual bearing is located in a bearinghead that can be displaced using guides extending parallel to the axisof the roller. The process takes place by means of a piston cylinderunit. The unit consisting of the bearing, the mandrel-mounting element,the guides, and the piston cylinder is often also referred to asmandrel-locking unit.

However, the disadvantage of this design is that the mandrel-lockingunit has an overall depth that results from its design and that iscomposed of the depth of the bearing piston and the maximum stroke ofthe piston cylinder unit. This overall depth brings about a spacerequirement on the operating side of the printing machine. This spacerequirement has a restrictive effect on the comfortable operability ofthe printing machine.

The patent application U.S. Pat. No. 3,147,702 suggests a similarmandrel-locking unit in which, however, it is not the bearing, butinstead the roller journal that is pulled off from the roller. The shaftjournal is thus a component of the mandrel-locking unit. In thisarrangement, the shaft journal is surrounded by the piston that isdesigned as a hollow space. However, this mandrel-locking unit alsoexhibits the disadvantage of a large overall depth.

Therefore, the objective of the present invention is to suggest amandrel-locking unit that has a more compact design and a lower overalldepth.

This objective is achieved by a mandrel-locking unit having thecharacteristics specified in the main claim 1.

Here, the boundary surface, as mentioned in the preamble of the mainclaim, is the part of the surface of the piston that delimits thepressure chamber of the pressurizing medium cylinder.

The mandrel-mounting element is a component that is suited for thepurpose of mounting the mandrel on the mandrel-supporting surface. Sincethe mandrel is supported on its supporting surface with the help ofbearings, it is also usually embraced by this bearing. As a rule, themandrel-mounting element is designed as a sleeve. In order to slide themandrel-mounting element, it is connected to the piston at a connectingpoint.

In a first advantageous embodiment of the present invention, thedistance between the boundary layer and the connecting point is smallerthan three quarters of the maximum stroke of the piston in the cylinder.

In a second particularly preferred embodiment of the present invention,the distance between the boundary surface and the connecting point issmaller than half of the maximum stroke of the piston in the cylinder.Such an embodiment provides a good compromise between a compact designand a secure guide of the mandrel-mounting element in the guide sleeve,for instance, to prevent a tilting effect. Of course, the distance canalso be significantly smaller.

Another advantage of this embodiment of the present invention is that,if enabled by the design, the displacement area of the mandrel-mountingelement and the pressure chamber into which the piston can move, mergeinto one another in the axial direction. In this manner it is possible,among other things, to completely omit the use of the piston rod that inknown mandrel-locking units is at least as long as the maximum stroke ofthe piston.

In case the pressure chamber and the displacement area merge into oneanother, it is advantageous if the inner diameter of the pressurizingmedium cylinder is larger than the outer diameter of themandrel-mounting element.

In this manner a direct transfer of force is ensured from the pistononto the mandrel-mounting element.

It is particularly advantageous if the piston is a disk without a pistonrod. Since the mandrel-mounting element would then take over the guidefunction of the piston rod, the former must be provided with a largeroverall length than the maximum stroke of the piston.

In order to ensure a secure connection between the piston and themandrel-mounting element, it is advantageous to provide a screwedconnection between these two elements.

In a third advantageous embodiment of the present invention, both themandrel-mounting element as well as the pressurizing medium cylinder aredesigned as circular cylinders. The axes of symmetry of these twocircular cylindrical components extend parallel to one another, withoutbeing aligned with one another. Thus the result is an easy acentralconnection between these two components with the advantage that themandrel-mounting element can be arranged on one side of the guidebushing. In a printing machine with an interaction of two print rollershaving a small outer diameter, the minimum outer diameter is determinedby the dimensions of the mandrel-locking unit. Should themandrel-mounting element be arranged in a displaced manner, the minimumdistance can be reduced again so as to enable the reduction of theminimum print repeat range of the printing machine.

The present invention can be used advantageously in flexographicprinting machines or gravure printing machines. However, it can also beused in printing machines that operate according to other principles.

A preferred embodiment of the present invention is set forth in thefollowing description in conjunction with the drawing, of which theindividual Figures illustrate:

FIG. 1 a mandrel-locking unit according to the invention with enclosedmandrel-supporting surface,

FIG. 2 a mandrel-locking unit according to the invention with a releasedmandrel-supporting surface,

FIG. 3 view of the section along III-III of the mandrel-locking unitillustrated in FIG. 1.

FIGS. 1 and 2 illustrate a mandrel-locking unit 1 substantiallycomprising a pressurizing medium cylinder 2. The pressurizing mediumcylinder 2 has a pressure chamber 3 into which a piston 4 can be slid.The piston 4 has on its outer circumference a sealing ring 5 that, as isknown, prevents compressed air from one side of the piston 4 fromreaching its other side. The compressed air is fed into the pressurechamber 3 by the compressed air inlets 6, 7. The pressurizing mediumcylinder 2 has, in addition to the pressure chamber 3, a guide area 8 inwhich the mandrel-mounting element 9 is supported slideably. Thepressure chamber 3 and the guide area 8 are separated from one anotherby the mandrel-mounting element 9 and the sealing ring 10. In onesection with an extended inner diameter, the mandrel-mounting element 9supports a bearing 11, for instance a roller bearing that can enclosethe mandrel-supporting surface 12 of the print roller mandrel 13. Inorder to transfer the force that acts due to the supply of compressedair on the piston 4 onto the mandrel-mounting element 9, both componentsare connected to one another in a manner that is not illustratedelaborately here. This connection is formed advantageously by using ascrew.

In the operating state illustrated in FIG. 1, compressed air is appliedto the pressure chamber by means of the compressed air inlet 6 so as tomove the piston 4 in the axial direction onto the print roller mandrel13. The guiding of the mandrel-mounting element 9 in the pressurizingmedium cylinder 2 ensures the axial guiding of the piston 4. During theprinting operation, pressure is applied to the pressure chamber 3 so asto prevent any unwanted separation of the bearing 11 and themandrel-supporting surface 12.

In order to achieve the operating state illustrated in FIG. 2,compressed air is applied to the pressure chamber by means of thecompressed air inlet 7 so as to move the piston 4 and with it themandrel-mounting element 9 away from the print roller mandrel 13 andinto its end position illustrated in FIG. 2. After the release of themandrel-supporting surface 12, the print roller mandrel 13 and themandrel-locking unit 1 can be moved in relation to one another. In theillustrated embodiment, the mandrel-locking unit 1 is moved in thedirection of the arrow x. For this purpose the pressurizing mediumcylinder 2 has a break-through 14 at at least one point.

FIG. 3 illustrates the arrangement of the piston 4 and themandrel-mounting element 9 that can be displaced easily in order tominimize the distance between the mandrel-mounting element 9 and theouter edge of the pressurizing medium cylinder 2 on the side of thebreak-through 14. List of Reference Symbols 1 Mandrel-locking unit 2Pressurizing medium cylinder 3 Pressure chamber 4 Piston 5 Sealing ring6 Compressed air inlet 7 Compressed air inlet 8 Guide area 9Mandrel-mounting element 10  Sealing 11  Bearing 12  Mandrel-supportingsurface 13  Print roller mandrel 14  Break-through x Direction ofmovement of the mandrel-locking unit

1. Mandrel-locking unit (1) for a rotary printing machine with amandrel-mounting element (9) that forms a hollow body and accommodatesin an enclosed form in its interior a bearing (11) for mounting a printroller mandrel (13) having a mandrel-supporting surface (12) and thatcan be slid between a mounting position in which the print rollermandrel (13) is in mesh with the bearing (11) and a release position inwhich the print roller mandrel (13) is out of mesh with the bearing(11), a pressurizing medium cylinder (2) comprising a pressure chamber(3) and a piston (4) located inside it for sliding the mandrel-mountingelement (9) between the mounting position and the release position,where the piston (4) delimits the pressure chamber (3) at a boundarysurface and is connected to the mandrel-mounting element (9) at aconnecting point for the transfer of the force required for sliding themandrel-mounting element, characterized in that the distance between theboundary surface and the connecting point is smaller than the maximumstroke of the piston (4) in the pressurizing medium cylinder (2), thatthe inner diameter of the pressurizing medium cylinder (2) is largerthan the outer diameter of the mandrel-mounting element (9) and that thepressurizing medium cylinder comprises a break-through (14) that is openin the release position of the mandrel-mounting element (9) so that theprint roller mandrel (13) and the mandrel-locking unit (1) can beseparated from one another by a movement in relation to one another. 2.Mandrel-locking unit (1) pursuant to claim 1 characterized in that thedistance between the boundary surface and the connecting point issmaller than three quarters of the maximum stroke of the piston (4) inthe pressurizing medium cylinder (2).
 3. Mandrel-locking unit (1)pursuant to claim 1 characterized in that the distance between theboundary surface and the connecting point is smaller than half of themaximum stroke of the piston (4) in the pressurizing medium cylinder(2).
 4. Mandrel-locking unit (1) pursuant to claim 1 characterized inthat parts of the mandrel-mounting element (9) can be displaced in thepressurizing medium cylinder (2).
 5. Mandrel-locking unit (1) pursuantto claim 1 characterized in that the piston (4) is a disk without apiston rod.
 6. Mandrel-locking unit (1) pursuant to claim 1characterized in that the connecting point between the piston (4) andthe mandrel-mounting element (9) has a screwed connection. 7.Mandrel-locking unit (1) pursuant to claim 1 characterized in that themandrel-mounting element (9) and the pressurizing medium cylinder (2)are shaped as circular cylinders and that their axes of symmetry extendparallel to the distance between one another.